“State” refers to a mode or condition of being. Anesthesia and sleep are examples. As state-based (rather than organ-based) medical specialities, the considerations of anesthesiology and sleep medicine are broad, encompassing all organ systems. While there is much other common ground between them, some of the most important concerns shared by the two specialties relate to a third state – the state of pain. The perioperative period provides a context in which these concerns are paramount, as adequate analgesia, restorative sleep and uncompromised ventilation are basic postoperative aims which must be carefully addressed to resolve potential conflicts between them. These issues provide themes for the upcoming annual meeting of the Society of Anesthesia and Sleep Medicine (SASM) in San Francisco on October 11 and 12, 2013.

Perioperative pain disturbs sleep and ventilation. Controlling it requires strategies that either circumvent the need for opioids and other sedating drugs or, where they are used, ensure that analgesia is achieved without undue depression of respiration or arousal responses.

The relationship between pain and disturbed sleep is bi-directional. Pain disturbs sleep and disturbed sleep appears to exacerbate pain, probably through central sensitization.1 Fibromyalgia is a condition that appears to involve such a mechanism, with neuropathic pain a common feature and sleep disturbance ubiquitous.2,3 Significant insomnia is seen in over half of patients with chronic back pain and almost 90 percent of pain patients have at least one sleep complaint.4,5 Pain complaints and sensitivity to heat stimuli increase in sleep- restricted volunteers; these effects are reversed by catch-up sleep.6,7 Self-reported short sleepers have reduced thresholds to noxious stimuli.8

Interestingly, melatonin – the hormone of sleep – appears to have a positive impact on pain. It may help reduce pain and sleep disturbance in fibromyalgia and other chronic pain syndromes.9 There is some evidence to suggest management of sleep disorders may improve pain symptoms.10

Almost 80 percent of patients undergoing chronic opioid treatment for non-malignant pain have sleep-disordered breathing, severely so in half of these.11,12 It can be obstructive and/or central in nature. The central component may involve hypoventilation or breathing periodicity. Irregular (ataxic) breathing patterns are commonly seen during sleep in patients taking opioids. Opioid-related suppression of arousal responses increases vulnerability of such patients to prolonged events during sleep or sedation.

Non-invasive positive airway pressure therapies have much to offer these patients during sleep: continuous positive airway pressure for obstructive sleep apnea; bi-level ventilatory support for sleep hypoventilation; and a newer mode – adaptive servo ventilation (ASV) – for breathing periodicity. ASV increases pressure support during the waning/hypoventilatory phase of periodic breathing and decreases it during waxing/hyperventilatory phase. This varying pressure support reduces the variability in ventilation, which counteracts the self- perpetuating source of the instability itself – the changing CO2 set point for ventilation between the high thresholds of sleep (which encourage hypoventilation) and the lower thresholds that accompany the arousals often seen during the hyperventilatory phase.

This is a rich mix of considerations that are of the first importance to anesthesiologists and to sleep physicians. Needless to say, that makes them core business for SASM. Acute aspects are going to receive close attention at our 2013 Annual Scientific Meeting on October 10-11 in San Francisco immediately before the ANESTHESIOLOGYTM 2013 annual meeting. Our meeting theme is “Opioids, Respiratory Depression and Sleep Disordered Breathing: Perioperative Implications.” We have assembled an expert faculty and the meeting will present a stimulating and relevant examination of these inter-related problems. Details are available on our website (www.sasmhq.org). Please note that Thursday will be devoted to workshops and Friday to the main body of the presentations, so for those who get in late, Friday is complete in itself. The society dinner on Thursday evening will feature Dr. Ralph Lydic as guest speaker with Jane C.K. Fitch, M.D. the ASA President-Elect, joining us as a special guest. We hope you will join us.

David R. Hillman, M.D. is Head, Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, and Director, West Australian Sleep Disorders Research Institute, Perth, Western Australia.